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unassimilatible writes "NASA has successfully tested a small-scale aircraft that flies solely by means of propulsive power delivered by an invisible, ground-based laser. How far away can in-flight IP/LASER broadband be?"

One of the hallmarks of classic science fiction, Larry Niven & Jerry Pournelles' "The Mote In Gods Eye" [amazon.com], proposes this very thing. The opening sections of the book are based upon on premise: lacking true FTL travel, an alien race reaches a human colony by building humungous lasers in their asteroid belt and planet surface, and using them to propel a light sail armed interstellar craft between stars.
Good book all around, and it's cool to see decent Science Fiction become more than just speculative drivel (it's one of my favourite books).

building humungous lasers in their asteroid belt and planet surface, and using them to propel a light sail armed interstellar craft between stars.

IANAP (I am not a physicist), but isn't using light pressure in a vacuum to drive a light sail entirely different from an aircraft with "specially designed photovoltaic cells carried onboard to power the plane's propeller"?

It's like (poor analogy alert) saying that a gasoline powered car and a squeeze-jet that squirts out liquid gasoline to propel itself through the water are using "the same" propulsive technology.

BTW, light sails were proposed by real physicists long before Niven and Pournelle wrote the excellent Mote in God's Eye.

Niven & Pournelle's Footfall [amazon.com] is a closer match. Aliens invade Earth and during the occupation, use ground-to-orbit shuttles that are partially launched by ground-based lasers. The lasers push the shuttle to an altitude where it's "safe" to crank up the main engine. Some resistance fighters manage to damage one laser ground-station during a launch, causing the loss of the shuttle, but they're subsequently creamed by the mothership. I don't remember if the shuttles glide to land, or come down ass-fir

I think that the "Angel's Pencil" (one of the first ships to encounter Kzinti) used a laser-based travel mechanism. Similar idea, but instead of the ship being fired into space by a big frickin' laser, it had one mounted which it used to bounce off various things for propulsion?

In latter books, it mentioned using lasers to propel cargo/cargo-ships around.

And the bonus is, of course, that when we are attacked by a carnivorous intelligent giant cat-species, we can use the lasers to fight back...

And the bonus is, of course, that when we are attacked by a carnivorous intelligent giant cat-species, we can use the lasers to fight back..

When the Kzin first encountered humans, the Kzinti telepath assured his commander (Chuft-Captain?) that the humans had no weapons, because that was what he read in the humans' minds. He also opined that human might be tasty (even though given that the telepath wasn't a warrior, and so was despised, he'd never taste any).

Laser driven Space Sails (ok not solar in this case, but light-driven, although they would prob use solar as well) use the momentum of the photons to push the craft forward - but you still need a damn powerful laser to do it effectively..

Laser driven space sails are one of the few feasable technologies we really have that could be used for sending probes interstellar distances in a viable time-scale.

I understand the acceleration part, but how would such a craft decelerate?

It won't have lasers at the place it's going to if it's unexplored, so...

My (novice) idea is to have a system of mirrors. The lasers can still point directly at the craft, but the mirrors will be like a cone deployed at the butt of the craft when it wants to start decelerating. There'd be another ring, like a cone with the top cut off, farther away from the craft, so the laser will bounce off the butt, hit the ring and bounce t

Not going to work, Im afraid. You can deflect the photons at an angle and get the force to steer left/right a bit, but never against the direction of the photon wind.

Your best bet is to turn around and use the light from the destination star to decelerate - if the destination is a binary, maybe some complex orbit would allow you to loop both stars until a slow speed is achieved.

Thats ok, and the answer is yes - the laser will feel a
reaction. Photons of light actually have weight. From memory,
about 2 pounds of sunlight falls on Earth each day. Not much
weight, but a heck of a lot of energy.

So in space, where there is no friction, a Solar
sail [google.com] can accelerate indefinately, but only in the direction
of the prevailing photon wind- to do it all with sun-power would
require huge sails, or you could use a smaller sail and
supplement it with drive from super-accurate laser power, mayb

I would guess both - I think the designers realise that there will be micro-meteor holes in the sail, also less particles will slow the sail down somewhat. A lot depends on the density of particles in interstellar regions, anyone got a more definative answer? I would guess that would be one reason we are travelling into interstellar space!

But the big problem with laser power beaming is stuff like clouds, and fog...

, people...

Nah, people are no problem. Cuts through them like a hot knife through butter. No problem at all.:-)

Actually you wouldn't want to be within a mile or two of a 100MW laser. It blinds just from diffusively scattered light at about that range- further than that if you use magnifying optics like binoculars.

Curvature wouldn't be too much of a problem if the laser (with big solar panels) was in orbit, pointing more or less straight down... OK, so punching a serious amount of power down through the atmosphere will cause all sorts of unwanted side effects, but no worse than point-to-point transmission across the surface.

Use the right frequency of laser or microwave, and clouds needn't be much of a problem. Come to think of it, if the thing (or part of it) were tunable, it could probably be used to make clouds d

Use the right frequency of laser or microwave, and clouds needn't be much of a problem. Come to think of it, if the thing (or part of it) were tunable, it could probably be used to make clouds disappear... And birds... And airplanes... And ICBMs...:)

If it can make clouds disappear, I imagine it wouldn't be too far of a stretch to have it (1) make clouds appear, and (2) make air currents hotter/colder, and thus have a shot at making tornadoes and hurricanes disappear... no doubt it's a huge amount of powe

That's not the intention at all, at least for now. They are just demonstrating a technology and debugging it. Usefull applications are just speculation at this point, and don't have to involve that kind of altitude. For example, instead of erecting an atenna or camera tower, one could put them in orbit around an equipent truck at just a hundred feet altitude. How well this compares with just hanging the stuff from a tethered balloon, I'm not sure.

Well...
At least over at Claude Bernard, Lyon 1 University in France, they have demonstrated a data carrier laser system which can penetrate clouds and fog.
I imagine som ecomercial application of that would be useful here.

Let's hope it's very, very far off. A laser beam pointing to/from a commercial aircraft is essentially a giant pointer, constantly updated, announcing the precise position of the plane. It should not be difficult at all to build a guidance system that follows the laser and delivers a payload to the plane just as a line climber [intothewind.com] follows a kite string to a kite. Said payload is not likely to be an emergency delivery of peanuts and soda.

A laser beam pointing to/from a commercial aircraft is essentially a giant pointer, constantly updated, announcing the precise position of the plane. It should not be difficult at all to build a guidance system that follows the laser and delivers a payload to the plane just as a line climber [intothewind.com] follows a kite string to a kite.

Hmmm, a system capable of tracking the precise position of an aircraft? You mean like RADAR?

I think you're talking FUD. We already have laser guided bombs/missiles, we've used them in the past 2 'conflicts' we've engaged in. Plus, this thing is invisible, so it's not like we're taking a visible beam of light to it. Adding a signal to the laser beam should be trivial...fast switching on and off to represent data.

They directed a laser beam at photaic cells? Nice other name than solar panel. OK, the laser powered plain flies as long a laser hits it. But still the plain is carrying it fuel (photaic cell aka solar panel) on board, as meantion in the introduction. This is no breakthrough but rather a toy for big children.

i hope this was sarcasm since most modern missiles use laser to target these days...

<military-pedantic>I'm not sure which "most missiles" you're referring to. If you're speaking in-context and on-topic, you're talking about surface-to-air antiaircraft missiles, and I'm not aware of any laser-guided ones in any world inventory. Most missiles in this class are guided by infrared detection or radar guidance (external, from a radar emitter on the ground, or internal, from an on-board radar set.)</mili

Surface-to-air, you can paint an aircraft with radar a lot farther out than you can with a laser beam. Sure, it's easy to tell when radar is tracking you, but you can track any laser powerful enough to guide a missile, too. Hell, I've got a laser detector in my car.

All in all, laser makes a pretty lousy guide for an air intercept missile.

Just one observation, from someone who works in the area. The aperture of your radar beam is typically very large compared to a laser, so you tend to light up the e

One of the major problems with moving anything from place to place is getting energy to move it. That energy typically comes from partial conversion of matter (liquid oxygen, gasoline, coal, hay, etc.), and that matter in turn tends to be carried along with whatever you're moving. That matter in turn needs energy to move it, and in some cases this amounts to a rather offensive amount of overhead (e.g., Saturn V).

There are two ways of handling this. One is to get the most efficient conversion possible, t

I first read about this sort of thing back in the 1970s. Proposals back then focused on constructing huge satellites (think 5 miles by 5 miles or 10 KM by 10 KM) in geosynchronous orbit. Energy would be beamed to earth via microwaves or lasers.

From the article:The plane, with its five-foot wingspan, weighs only 11 ounces and is constructed from balsa wood, carbon fiber tubing and is covered with Mylar film, a cellophane-like material.... The lightweight, low-speed plane was flown indoors at Marshall to prevent wind and weather from affecting the test flights.... Without the need for onboard fuel or batteries, such a plane could carry scientific or communication equipment, for instance, and stay in flight indefinitely.

If the laser uses the right frequency, such as some forms of infrared, clouds will be transparent to it.

I think this has it's best use in forms of helping a pilot who has run out of fuel. If planes move to fuel cell propulsion (There is a small fuel cell powered plane on the market now!) in the future, as they will once the technology is perfected in cars, if a pilot is running low on power, he can request a laser assist to limp to the nearest airport.

There is another laser powered craft that is much simpler. In fact, it has no moving parts. It looks like a fancy chrome plated frisbee, and is about that size. They get it spinning fast on the ground and then start shooting a laser at it from below. The disk is shaped such that the laser is reflected and a small chamber is heated, causing the air inside to expand, pushing air through a nozzle. The spinning gives it stability and the laser provides propulsion.

I saw it on a PBS show about advanced propulsion devices a few years ago. Very much a research project, and not currently capable of carrying a payload, but interesting for its simplicity (in the craft at least).

I came up with this idea as a rocket propulsion many years ago while pondering the best way to get a rocket up. Go to Huntsville, AL sometime and walk along the Saturn V that's laying down there, and keep in mind that most of the fuel is simply lifting other fuel. By the time you get to the end of it, and realize that the tiny capsule is the payload, you know there's gotta be a better way. Keeping the bulk of the propulsion system ground based would allow you to fly something little bigger than a capsule

Here [space.com]is a different solution (from back in '99) using a conical mirror to focus a high-powered laser and ignite the air underneath it to generate propulsion. Perhaps not generally useful yet, but perhaps more generally applicable than charging solar-cells with a laser.

Lightcraft Technologies Inc. have been flying laser-powered craft since 1997 their heighest flight reached a 233ft in October 2000.

Their technolnogy is rather different to nasa's photon-pushed leightweight design, instead they have a 1-kilo spinning-top that has a curved mirror on the bottom, which focuses very short laser pulses from the ground to heat the air under the spinning top to extreme temperatures, 'blasting' the top upwards.

Sadly, their website (www.lightcrafttechnologies.com) was last updated

What effects would a power laser beam have on surface stuff (people, computers, animals, plants, etc.)?

What if we had huge, tethered balloons, up several miles as receivers for space based power production. Could you use lower power transfer beams, since you wouldn't have to go through the lower 5-10 miles of atmosphere? You'd then pipe the electricity down to ground based distribution station

Ever since the dawn of powered flight, it has been necessary for all aircraft to carry onboard fuel - whether in the form of batteries, fuel, solar cells, or even a human "engine" - in order to stay aloft.

But a team of researchers from NASA......is trying to change that

But how does it work Bob:

The laser tracks the aircraft in flight, directing its energy beam at specially designed photovoltaic cells carried onboard to power the plane's propeller.

The basic problem is the laser: lasers are inefficient. For nearly every laser currently available, 99.9% of the energy you use to pump the laser goes into heat; only a small fraction is converted to coherent light.

Current laser designs are capable of delivering watts of power, at the cost of kilowatts of energy. A few watts, even a few hundred watts is barely enough to power the map light in a plane/space capsule/whatever, let alone make it fly.

While the article may be correct that this is the first time a plane has been powered by laser light, there was the SHARP project [friendsofcrc.ca] that flew a plane powered by a microwave beam. It was fitted with a special microwave receiver that converted the beam directly to DC current. This project was envisioned to be used for communication platforms too. I wonder which version would be more energy efficient?

(obligitory obvious prior art posting to prevent people from patenting this stuff) Isaac Asimov "I, Robot".. a space-based power station near the sun that beams the solar energy back to earth. Major plot that the station is taken over by a "religious" robot.

You consider a DC-3 full of backup tapes "broadband" otherwise that was just a sad non sequiter. Broadband and power over laser are two different technologies and have very different hurdles to surmount before being practical. Progress in one area does not neccicarily cause progress in another. Kids, we're loosing touch with reality, there are things that don't revolve around broadband. (I think)

I can't believe NASA is getting press over this. It is a solar powered model airplane that has its solar cell power output increased by shining a laser on it. I expect to see this sort of thing at a high school science fair; not flight tested at both Edwards and Marshall (so that the engineers at each location could get some free travel, no doubt). It looks to me as if someone needs their budgets cut. Keep this waste of tax dollars in mind next time NASA complains that unless they get more money then th

When was the last time you saw an invisible laser.. lasers are in the visible light spectrum

I'm not a physicist, but I've seen lots of inivisble lasers (okay, not the beam itself, but you know...). Lasers in both the infrared and ultraviolet regions are commonplace. Google for "infrared laser" or "ultraviolet laser" and you'll find many, many examples of each.

I suppose you could make some sort of argument that the L in LASER if for "light," and that IR and UV somehow aren't light because we can't see them. But insects and perhaps some animals can see in those regions, so it'd be a difficult position to defend. Both IR and UV are called "light" in general use. Additionally, there's no significant physical difference between a visible light laser and a UV or IR laser. And scientists now use the term "laser" even where most people would agree that the electromagnetic energy in question falls outside the part of the spectrum that we tend to think of as "light," e.g. x-ray lasers [optics2001.com] and microwave lasers [achilles.net].

One of the greatest EM scientists of all time.. who for some odd reason isn't mentioned in ANY western schools.

Don't be ridiculous. I doubt very much that you can find a freshman physics class in the western hemisphere where Nikola Tesla isn't mentioned. And I don't remember visiting a science museum that didn't have a giant Tesla coil. The man's name is an International Unit for heaven's sake.

I have an Associate's Degree in Laser Electro-Optic Technology. Any oscillator that produces electromagnetic radiation in the range of infrared or shorter wavelengths by the process of stimulated emission of radiation is considered a laser. In fact, the name has become shorthand for just about anything that produces a beam of anything through quantum

Brief interruptions, such as those caused by birds or other objects flying into the beam would not cause the plane to crash. No need for batteries, just glide past the interruption, and as long as you can reacquire the beam you won't have any problems.